Structured polymers and copolymers have attracted considerable attention over the past decades due to new and improved properties of the resulting polymers. The term “structured” as used herein with respect to synthetic polymers is intended to designate non-linear polymers.
Polymers such as acrylamide polymers have been used throughout the papermaking process as dry strength agents, drainage agents, retention aids, coagulants, dispersants, etc. Dry strength is an important property, which must be met at some minimum level to meet the end use for paper and paperboard products. Acrylamide containing polymers are well known in the paper industry to provide dry strength. Linear acrylamide polymers having a weight-average molecular weight range from about 50,000 to somewhat greater than 5,000,000 have conventionally been used as dry strength agents. Existing acrylamide based commercial examples include acrylic acid (AA)/acrylamide (AcAm) copolymer, glyoxalated diallyldimethylammonium chloride (DADMAC)/AcAm, and an amphoteric polymer composed of AcAm/itaconic acid/dimethylammoniumethylmethacrylate (DMAEM)/dimethylammoniumethylacrylate benzyl chloride quat (DMAEA BCQ). These commercial strength agents suffer from various drawbacks including handling issues, paper machine process issues or inadequate dry strength. Demands in modern paper industry have resulted in need for improved dry strength agents. In addition to allowing papermakers to achieve their product strength specifications, the dry strength additive enables papermakers to reduce basis weight, substitute low cost fiber, increase filler loading, increase machine speeds and modify sheet properties.